[ErrantX]

It's entirely logical: you just have to think outside the box (big enough baloon vs. small enough vehicle: plus it overcomes some of the niggly "near ground" effects [why do you think so many next-gen space vehicle designs launch from Airplanes??])

The physics is there and probably workable.

(EDIT: my initial thoughts would tend towards a high altitude launch of several smaller sized vehicles that re-assemble on the lunar surface... or interact there. S o for example someone above mentions the comms issue: a static relay planted on the surface interfacing with a seperate rover device would probably work well. In fact I would launch 2 or 3 of each type (assuming cost could be kept low) to ensure that you got at least one functioning pair :D)

[stcredzero]

Jet airplanes also give you something like 600 mph of initial velocity. In the case of Pegasus and Space Ship One, they are like the first stage rocket.

The Rocket Equation is pretty nasty. When your required delta-v goes up, your reaction mass requirement goes up faster than a polynomial function. Saving the initial 600 mph is very significant. Balloons -- only sounding rockets use those, but they don't do anything but gain altitude anyhow. If you need escape velocity or orbit, then they are pretty much useless. (You might as well build a slightly bigger rocket.)

Please actually do the physics before you post vacuous statements like:

The physics is there and probably workable.

People are having "intelligent discussions" about balloon assisted launch? Eternal September has gotten to HN!

[ErrantX]

I have done the physics: or spoken to people that have.

In fact I have seen a successful small rocket launched from a 100 ft high ballon platform (the physics is painful but it is possible).

Other ideas like centrifuge acceleration I know have been discussed: and I personally see potential in them (Ammers & Myers, Oxford University Press, 2006 I think: I'll try and dig out a reference #).

With equal respect I suggest you actually try to think outside the box before posting vacuous statements stating it is impossible.... ;)

EDIT: BTW you do know NASA have recently been exploring the possiblity too.... admittedly for low earth orbit sattelites (and i know that a major problem is breaking that barrier - but it is proof of an initial concept....)

The crucial data is that ballons can carry rockets to a MUCH higher altitude than planes. The reduced drag at that altitude means a lot less propellant is needed (and even a solid fuel propellant could suffice).

NASA has plans for a ballon that can carry up to a ton of equipment to a height of 33Km which is pretty good!

You've also missed the point of the airplane: 600MPH is frankyl nothing (4% of the speed required for LEO). The important thing is the lowered drag and kinetic requirements to get the payload to LEO.

[gravitycop]

You've also missed the point of the airplane: 600MPH is frankyl nothing (4% of the speed required for LEO).

Small increases in speed would indeed be relatively unimportant in regard to only a final stage. When, instead, an increase in speed affects an entire rocket stack, it becomes important, since lower stages are exponentially more massive than upper stages. For the same reason, it can be important to launch from the equator, since equatorial launch provides 465 m/s of speed, not only for the final payload, but for the entire rocket stack.

[gravitycop]

I have seen a successful small rocket launched from a 100 ft high ballon platform

That was a sounding rocket. As Stcredzero wrote in the message you responded to, "Balloons -- only sounding rockets use those." http://en.wikipedia.org/wiki/Sounding_rocket

http://www.astronautix.com/lvs/rockoon.htm

[ErrantX]

I present to you Cambridge University no less...

http://en.wikipedia.org/wiki/CU_Spaceflight

And NASA are at work on a system to launch pico and micro satelites in near earth orbits.

[gravitycop]

I present to you Cambridge University http://en.wikipedia.org/wiki/CU_Spaceflight

Why are you presenting that? Did you read that page? It discusses the launching of sounding rockets (rockets that go up, not into orbit). Is there anything about orbital launch, or orbital speed, there?

[ErrantX]

Well HN I am a bit disappointed in this "cant be done" give up attitude... I assure you it can and will be done.

I assumed you'd have the initiative to follow the links and read up on CU Spaceflight.... but apparently not (hint: that was a hint).

If that's not good enough then lets go with NASA... http://academy.grc.nasa.gov/2008/group-project/new-launch-te...

They also have a design for a ballon to reach 110,000 feet which could carry up to a ton of equipment. I'm thinking centrifuge or "gun" launch at the altitude might go well :D